Wednesday, January 11, 2017

Ex position switches.

Offshore industry knows no fewer than four factors which make extreme demands on switchgear. There is a risk of explosions; switches are exposed to high levels of mechanical wear and tear; the environment is corrosive; and it can be very cold.

These position switches from Steute, with dimensions to DIN EN 50047, have been tested and approved according to ATEX and IECEx for use in gas Ex zones 1 and 2, as well as dust Ex zones 21 and 22. They can be used in temperatures as low as -60°C, which is very demanding on housing construction and sealing. For example, it must be guaranteed that the switchgear's high protection class (IP 66) will be maintained in these subzero conditions at all times, even after a 7-Joule impact test.

For this reason, the stable housing is manufactured from high-quality fibreglass-reinforced plastic. The sealing of the housing cover is completely vulcanised, while the sealing of the plunger features a redundant sealing system, comprising an external sealing cuff able to withstand low temperatures and an internal Teflon sealing ring.

The sealing materials have been cleared by their manufacturers for temperatures down to -95°C, and the lubricants down to -75°C. There is therefore a sufficient "tolerance" to the steute-approved temperature of -60°C. This gives users the certainty that the new position switches will work reliably even in truly extreme ambient conditions.

Due to a comprehensive range of actuators (plunger, roller plunger, roller lever, parallel lever, turning lever, adjustable turning lever, push button…) and their compact dimensions, the Ex norm switches are very versatile and easy to integrate in a surrounding construction. They are available with slow-action or snap-action and, as an added bonus, earthing and potential equalisation are superfluous because of the protection-insulated plastic.

This set of features in the Ex 97 series makes it a good example of the "Extreme" switchgear developed by steute. It is suited not only to applications in the chemicals industry and energy technology, but also e.g. for position monitoring of flaps and valves in plants of the oil and gas industry (offshore and onshore), as well as on ships travelling through the Arctic.